量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.

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We examined whether cerebral vascular reactivity to 5% CO2/95% O2 would be a useful, independent measure of effects of tobacco smoking on global cerebral blood flow (gCBF). The acute effects during smoking one's favorite brand of cigarettes were determined after overnight tobacco abstinence. Positron emission tomography was used to quantitatively measure gCBF using H(2)15O in 10 right-handed young-adult male volunteer tobacco smokers. After a 12-hr abstinence, gCBF measurements were repeated six times at 15-min intervals: First baseline, 5% CO2/95% O2 inhalation, first cigarette smoking, second baseline, 5% CO2/95% O2 inhalation, and second cigarette smoking. Surprisingly, no significant change was seen in mean gCBF during smoking compared with baseline. However, the increase in arterial plasma concentration of nicotine correlated inversely with gCBF. Out of 19 smoking sessions, gCBF increased in 7, decreased in 7, and was unchanged in 5 sessions. The gCBF increased during smoking when baseline gCBF was relatively low, whereas gCBF decreased when baseline gCBF was relatively high. Both vascular reactivity and estimated gCBF plus arterial nicotine concentrations were useful measures to predict the changes in measured gCBF. These individual differences result in important bimodal effects of smoking on the brains of different young adult tobacco smokers.